1. Field of the Invention
This invention relates to bevel-gear diffential assemblies. In particular, it is concerned with such a differential assembly in which a limited slip capability is provided.
2. Description of Prior Art
There have been many proposals for limited slip differentials. Thus it is known to connect a viscous shear coupling across two parts of a differential gear. In this arrangement, restriction of the differential always takes place when there is a speed difference between the parts of the differential gear between which the viscous coupling is connected. This may provide problems in motor vehicles in which anti-lock braking systems are incorporated. Because of these problems it is common to keep the torque transmission through the viscous shear coupling low which, in some circumstances, means that there may be insufficient locking torque.
It is also known to have differential assemblies in which the restriction on differential action is effected by a friction coupling which is torque dependent. One disadvantage of this design is that the restriction takes place abruptly which may affect the directional stability of the vehicle. Sometimes the frictional coupling is pre-loaded but, when it is not, only acceleration torque may be usable.